Conventional antenna devices for use in contactless power supply through electromagnetic induction include a wide variety of antenna devices for power transmission such as those according to the Qi standard. Putting aside applications that require compatibility, such antenna devices are typically used as a pairing of an antenna device for power transmission and an antenna device for power reception that have roughly the same shape in consideration of magnetic coupling and productivity.
Recently, there has been a trend of mounting contactless power supply antennas on wearable terminals. In such a situation, there is a limitation on the mounted contactless power supply antenna in terms of the small volume allotted thereto because the size of the wearable terminal itself is also small. Accordingly, it is necessary to raise power transmission efficiency in contactless power supply within the bounds of this limitation.
Examples of combinations of an antenna device for power transmission and an antenna device for power reception that have been considered with the aim of raising power supply efficiency include configurations described in PTL 1 and 2. In these configurations, the antenna device for power transmission is a feed line and the antenna device for power reception is a coil that is wound around a core having a shape that surrounds the feed line.